The proposed Phase II SBIR research effort will continue our development and demonstrations of the synergistic use of spaceborne radar for tracking surface targets through fusion of SMTI between spaceborne and airborne radars. During the Phase I SBIR we developed a multiple hypothesis tracker (MHT), integrated HRR feature-aided tracking within our MHT, and performed simulations involving sensor fusion between airborne radar GMTI and spaceborne radar GMTI while using HRR for feature-aided tracking. These results demonstrated the utility of feature-aided tracking and the benefits of the synergistic use of spaceborne and airborne radar assets for tracking ground vehicles. Our proposed Phase II effort will: 1) enhance the realism of our spaceborne radar simulations by modeling specific candidate LEO and MEO spaceborne radar configurations based on demonstrated commercial technology, 2) investigate and develop techniques using Range-Doppler, ISAR, and SAR imagery to improve track metrics in difficult tracking situations such as multiple vehicles arriving simultaneously at a intersections and move-stop-move maneuvers, and 3) increase the complexity and revisit intervals of the tracking simulations. BENEFIT: The success of the proposed effort can play a major role in validating the utility of spaceborne radar for tracking surface vehicles. This technology is also applicable to airborne radars. We anticipate future business opportunities integrating this technology into battle-space simulation environments and airborne radar systems. Commercial applications include ship tracking and arctic sea ice tracking.